The invention is concerned with power tools, particularly, but not exclusively relatively lightweight power tools suitable for use by the general public.
A number of power tools are in general use in the handyman's do-it-yourself market, for example, power drills, saws and the like. However, those jobs involving breaking up hard materials such as concrete, slabs, stone or even heavy earth have not readily been tackled by anything less than a heavy duty or industrial tool as for example, a pneumatic drill.
The present invention further provides a portable power tool comprising a housing, a drive means and a mounting arrangement for a selected one of a plurality of interchangeable tool bits, wherein there is provided within the housing an output arrangement adapted to drive an output shaft in a reciprocal axial movement to drive a selected tool bit.
Advantageously the drive means may be a linear output motor. Alternatively, the drive means may be a rotary motor requiring the intermediary of a device, which may be a cam device, to convert rotary motion into axially reciprocating motion.
Conveniently, therefore, there may be provided a cylinder cam mounted for rotation with the output shaft from the motor, said cam being provided with a sinusoidal cam track extending around its circumferential surface, an output shaft adapted to partake of reciprocal axial movement to drive a selected tool bit, and cam follower means adapted to run in said cam track to impart said reciprocal axial motion to said output shaft.
Conveniently, the cylinder cam may be selected from a plurality of cam members having a range of cam throw distances.
Where necessary, intermediate gearing may be interposed between the motor and the output shaft. Conveniently, the motor may be powered by mains electricity using a transformer, or by batteries. If desired, the batteries may be of the rechargeable type or may be replaceable. In an example of the invention, the batteries may be incorporated into a detachable battery/handle module for rapid replacement. In another example mains power is provided by a detachable cable and a battery pack is provided for use in place of mains power when the cable is detached. Conveniently the batteries may be of the rechargeable type.
There will now be described several examples of devices according to the invention. It will be understood that the descriptions are given by way of example only and not by way of limitation.